TRANSPIRATION AND PHOTOSYNTHESIS OF SWEET PEPPER GROWING UNDER DIFFERING SCREENHOUSE NETS

The influence of three screenhouse nets differing in colour, shading intensity (SI) and porosity on photosynthesis, transpiration rate and light acclimation of sweet pepper plants was investigated at Velestino (central Greece) from May to October 2011. The screenhouse nets consisted of two insect-proof white nets (W13 and W34, SI=13 and 34%, respectively), and a green shading net (G36, SI=36%). Climate variables were recorded continuously in the different treatments. Leaf photosynthesis and transpiration rate were measured fortnightly over different canopy layers. The results indicated that drastic changes in light regime induced by shading nets had only a slight effect on leaf gas exchange and water use efficiency. Ontogenic effects (leaf ageing) appeared to be the main factor responsible for the observed seasonal pattern of leaf photosynthetic attributes. Overall, sweet pepper plants grown under screenhouse treatments appeared to display a physiological response and light-acclimation across a large interval of SI that was close to that observed for the field grown crop, irrespective of the colour and porosity of the nets.